Avista recognizes the role that healthy lakes, reservoirs and rivers play in providing important fish and wildlife habitat, and safe recreation opportunities for the public. As part of the Federal Energy Regulatory Commission's (FERC) Spokane River Project License, we have several ongoing water quality mitigation measures associated with our Spokane River operations in both Idaho and Washington, and we monitor several water quality parameters, such as total dissolved gas, temperature, and dissolved oxygen.

Total Dissolved Gases

Since 2010, Avista has been monitoring total dissolved gas (TDG) supersaturation in the forebays and tailraces at its Post Falls and Long Lake dams. To address TDG, we are looking into operational changes at the Post Falls Dam to reduce TDG levels and are currently investigating several different spillway modifications that may reduce TDG at Long Lake Dam.

Dissolved Oxygen

Avista is a participant in the Washington Department of Ecology’s Dissolved Oxygen Total Maximum Daily Load (DO TMDL) for the Spokane River and Lake Spokane (the reservoir created by Long Lake Dam). The DO TMDL is a water quality improvement plan that limits the combined amount of nutrients (i.e. phosphorus, organic matter, and ammonia) that can be discharged into the Spokane River from both point sources and non-point sources. As required by the FERC License and the DO TMDL, Avista developed a Lake Spokane Dissolved Oxygen Water Quality Attainment Plan (DO WQAP), which identifies potential reasonable and feasible measures to reduce phosphorus from non-point source loading around the lake. Avista's goal is to improve dissolved oxygen concentrations when Lake Spokane does not meet the state’s standard.

Stratification of Lake Spokane during the summer also impacts dissolved oxygen levels in the river immediately downstream of Long Lake Dam. In an effort to address this, we investigated methods to increase the levels of dissolved oxygen when the turbines are operating during the late summer months. In 2010, we field tested draft tube aeration equipment at Long Lake Dam in an effort to add oxygen to river below the dam. The results from the field test indicated dissolved oxygen concentrations met the state’s standard when water passes through the turbines. As a result, Avista plans to continue with the draft tube aeration and monitor the dissolved oxygen improvements each summer during low flows through 2016. The results of this monitoring are posted to the Water Quality Plans & Reports section below.

Avista also provides funding to the Idaho Department of Environmental Quality (IDEQ) and the Coeur d’Alene Tribe to complete water quality monitoring in Coeur d’Alene Lake. The water quality monitoring is completed in accordance with the quality assurance protocol established in the Coeur d’Alene Lake Management Plan, which was developed jointly by the Coeur d’Alene Tribe and IDEQ. Avista also provides funding to IDEQ for the Citizen Volunteer Monitoring Program to complete water quality monitoring at select locations on the Spokane River, upstream of the Post Falls Dam.

The water quality monitoring being completed in Coeur d’Alene Lake and in the Spokane River, upstream of Post Falls Dam, will aid IDEQ and the Coeur d’Alene Tribe in assessing water quality related to dissolved oxygen and associated nutrients. The results of this monitoring are posted to the Water Quality Plans and Reports section below.

Temperature

Avista completed a Long Lake HED Temperature Water Quality Attainment Plan (Temperature WQAP), which evaluated temperature impairments in Lake Spokane, as well as the river immediately below Long Lake Dam.

With regard to the the river immediately below Long Lake Dam, the depth of the powerhouse intakes, which are about 30 feet below the lake’s surface, results in cooler water being discharged downstream from the dam, as compared with Lake Spokane’s surface temperatures during the heat of the summer. The temperatures immediately below the dam consistently meet Washington’s temperature criteria. Farther downstream, Avista also works with the Spokane Tribe to implement and monitor improvements in water temperature in tribal waters.

As part of the Spokane River Project License, Avista is implementing water quality mitigation measures in consultation with various regulators, agency partners, and stakeholders.

Work plans, analyses, monitoring plans, and annual monitoring/summary reports associated with the water quality mitigation measures identified in the License are posted, and available for download. These include:

Communication and correspondence between Avista, its agency partners, regulators, and stakeholders is essential as Avista implements its water quality programs. The following FERC documents and agency correspondences are provided for your reference.